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To understand turbulent convection at very high Rayleigh numbers typical ofnatural phenomena, computational studies in slender cells are an option if theneeded resources have to be optimized within available limits. However, theaccompanying horizontal confinement affects some properties of the flow. Here,we explore the characteristics of turbulent fluctuations in the velocity andtemperature fields in a cylindrical convection cell of aspect ratio 0.1 byvarying the Prandtl number $Pr$ between 0.1 and 200 at a fixed Rayleigh number$Ra = 3 \times 10^{10}$, and find that the fluctuations weaken with increasing$Pr$, quantitatively as in aspect ratio 25. The probability density function(PDF) of temperature fluctuations in the bulk region of the slender cellremains mostly Gaussian, but increasing departures occur as $Pr$ increasesbeyond unity. We assess the intermittency of the velocity field by computingthe PDFs of velocity derivatives and of the kinetic energy dissipation rate,and find increasing intermittency as $Pr$ decreases. In the bulk region ofconvection, a common result applicable to the slender cell, large aspect ratiocells, as well as in 2D convection, is that the turbulent Prandtl numberdecreases as $Pr^{-1/3}$.

Similarities between characteristics of convective turbulence in confined and extended domains